1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to multi-piece golf balls having a center inner sphere, a center outer layer, a mid layer and a cover.
2. Description of the Related Art
Top concern to golf players for golf balls is their flight performances. The golf players particularly place great importance on flight distance attained upon shots with a driver.
The golf players also place great importance on flight distance upon shots with a long iron and a middle iron. The flight performance greatly depends on resilience performances.
The golf players place great importance also on spin performances of the golf balls. Great back spin rate results in small run. For golf players, golf balls which are liable to be spun backwards are apt to be rendered to stop at a targeted position. Great side spin rate results in easily curved trajectory of the golf ball. For golf players, golf balls which are liable to be spun sidewise are apt to allow their trajectory to curve intentionally. The golf balls that are excellent in spin performances are excellent in control performances. High-level golf players particularly place great importance on control performances upon shots with a short iron.
For golf players, stability of spin rate is also important. With a golf ball having variance of the spin rate, it is not easy to obtain the intended trajectory by the golf players.
Upon shots with an iron, the golf ball is rubbed with the face of the club. Due to this rubbing, the surface of the golf ball may be scuffed. Greatly scuffed golf balls can be no longer used. Scuff resistance performances are also important for golf balls.
In light of improvement of performances, a variety of proposals have been made with respect to golf balls. U.S. Pat. No. 6,123,630 (JP-A-10-328325) discloses a four-piece golf ball comprising a core having two-layer structure and a cover having two-layer structure. The core is formed by an inner sphere and an outer layer. The surface hardness of the core is less than that of the inner sphere. U.S. Pat. No. 6,248,027 (JP-A-10-328328) discloses a four-piece golf ball comprising a core having two-layer structure and a cover having two-layer structure. The core is formed by an inner sphere and an outer layer. The surface hardness of the core is less than that of the inner sphere.
Requirements for golf balls by golf players have been increasingly escalated in recent years. Balance of a higher order among the performances has been desired. An object of the present invention is to provide a golf ball that is excellent in the resilience performance, the spin performance, the spin stability and the scuff resistance performance.